The Original Job Requirements
The asphalt pavement was showing its age and was beyond practical repairs. The original job was to perform a 2.5-inch milling of the existing pavement and install an asphalt overlay. Asphalt overlays are a common, economical and effective way to bring an aging or damaged pavement back to life. Overlays are applied to existing pavements and, with proper maintenance, will look and last almost as long as new pavement.
The Challenges of the Job
For an overlay to be feasible, the foundation supporting the original pavement needs to be stable. While still in the early stages of the job, we realized that the foundation was far from stable. In fact, the integrity of the subgrade had been so compromised that our equipment began to sink. …show more content…
The analysis showed that the soil underneath the pavement was a type of vertisol, also known as gumbo. These types of soils tend to be very rich in silty clay, and when wet, the clay becomes quite sticky. Furthermore, clay swells during wet weather and contracts during the dry season. Repeated expansions and contractions allow the base and the pavement to move, resulting in extensive cracks, subsidence and potholes. In addition, gumbo tends to dry from the top down, which means that the top layer can be dry and deeply cracked, but underneath, the water remains trapped. The different layers of the soil begin to slip and slide, causing additional damages to the base and